This invention is directed to a method for producing on the surface of a fluorochemically treated substrate an antimicrobially active surface by exposing the substrate to a strong acid.
Antimicrobial agents are chemical compositions that are used to prevent microbiological contamination and deterioration of products, materials, and systems. Particular areas of application of antimicrobial agents and compositions are, for example, cosmetics, disinfectants, sanitizers, wood preservation, food, animal feed, cooling water, metalworking fluids, hospital and medical uses, plastics and resins, petroleum, pulp and paper, textiles, latex, adhesives, leather and hides, and paint slurries. Of the diverse categories of antimicrobial agents and compositions, quaternary ammonium compounds represent one of the largest of the classes of antimicrobial agents in use. At low concentrations, quaternary ammonium type antimicrobial agents are bacteriostatic, fungistatic, algistatic, sporostatic, and tuberculostatic. At medium concentrations they are bactericidal, fungicidal, algicidal, and viricidal against lipophilic viruses. Silicone quaternary ammonium salt compounds are well known as exemplified by U.S. Pat. No. 3,560,385, issued Feb. 2, 1971, and the use of such compounds as antimicrobial agents is taught, for example, in a wide variety of patents such as U.S. Pat. Nos. 3,730,701, issued May 1, 1973, and 3,817,739, issued Jun. 18, 1974, where the compounds are used to inhibit algae; 3,794,736, issued Feb. 26, 1974, and 3,860,709, issued Jan. 14, 1975, where they are employed for sterilizing or disinfecting a variety of surfaces and instruments; 3,865,728, issued Feb. 11, 1975, where the compounds are used to treat aquarium filters; 4,259,103, issued Mar. 31, 1981; and in British Patent No. 1,386,876, of Mar. 12, 1975 . Published unexamined European Application No. 228464 of Jul. 15, 1987, teaches that microorganisms on plants can be killed by the application thereto of an aqueous mixture of a surfactant and an organosilicon quaternary ammonium compound. In a particular application of an antimicrobial silicone quaternary ammonium compound, a paper substrate is rendered resistant to the growth of microorganisms in U.S. Pat. No. 4,282,366, issued Aug. 4, 1981. In U.S. Pat. No. 4,504,541, issued Mar. 12, 1985, an antimicrobial fabric is disclosed which is resistant to discoloration and yellowing by treatment of the fabric with a quaternary ammonium base containing an organosilicone. U.S. Pat. No. 4,615,937, issued Oct. 7, 1986, as well as its companion U.S. Pat. No. 4,692,374, issued Sep. 8, 1987, relate to wet wiper towelettes having an antimicrobial agent substantive to the fibers of the web and being an organosilicon quaternary ammonium compound. In a series of Burlington Industries, Inc. U.S. Pat. Nos. 4,408,996, issued Oct. 11, 1983, 4,414,268, issued Nov. 8, 1983, 4,425,372, issued Jan. 10, 1984, and 4,395,454, issued Jul. 26, 1983, such compounds are disclosed to be useful in surgical drapes, dressings, and bandages. This same assignee also discloses these compounds as being employed in surgeons' gowns in U.S. Pat. Nos. 4,411,928, issued Oct. 25, 1983 , and 4,467,013, issued Aug. 21, 1984. Organosilicon quaternary ammonium compounds have been employed in carpets, in U.S. Pat. No. 4,371,577, issued Feb. 1, 1983; applied to walls, added to paints, and sprayed into shoes, in U.S. Pat. No. 4,394,378, issued Jul. 19, 1983; applied to polyethylene surfaces and used in pillow ticking in U.S. Pat. No. 4,721,511, issued Jan. 26, 1988; in flexible polyurethane foams of fine-celled, soft, resilient articles of manufacture in U.S. Pat. No. 4,631,297, issued Dec. 23, 1986; and mixed with a surfactant in Japanese Kokai Application No. 58-156809, filed Aug. 26, 1983, of Sanyo Chemical Industries, Ltd., for the purpose of achieving uniformity of distribution of the compounds to a surface.
The antimicrobial agents described above are effective and versatile. However, their chemistry is complex. In the present invention, a simple approach is provided and an alternative to the previous complex techniques of the prior art.
It is not new to employ an acid to kill germs. For example, in copending U.S. patent application Ser. No. 187,151, filed Apr. 28, 1988, of Lynne Marie Blehm Blank, and assigned to the same assignee as the present application, acids are combined with quaternary ammonium compounds of the type above referenced, in order to provide a synergistic effect in combatting microorganisms. U.S. Pat. No. 4,034,079, issued Jul. 5, 1977, is representative of the use of boric acid. Lactic acid is taught in U.S. Pat. No. 4,084,747, issued Apr. 18, 1978, as a germ killing composition. In U.S. Pat. No. 4,737,405, issued Apr. 12, 1988, and in its companion U.S. Pat. No. 4,740,398, issued Apr. 26, 1988, there is disclosed leachable antimicrobial agents of acids such as citric, malic, sorbic, and ethylenediaminetetra-acetic acid. What has not been taught by the prior art and the concept of the present invention, is to employ strong acids to treat a particular type of substrate, the substrate having previously been fluorochemically exposed. Thus, in accordance with the present invention, a fluorochemically treated substrate is boiled in sulfuric acid thereby rendering a surface of the substrate antimicrobially active. This new and simple technique is not disclosed in the prior art.